The present invention relates to a method for producing a conductive polymer film suitable for, for example, enhancing electrical conductivity of a PEDOT/PSS film capable of being manufactured quickly and at low cost with simple operation, enhancing electrical conductivity of the PEDOT/PSS film significantly, and obtaining stable properties of the film.
When considering conductive polymer as industrial material, it is required that electric conductivity (hereinafter called conductivity), processability, and stability are above a certain level.
From this point of view, only polypyrrole, polyaniline, polythiophene (poly-3,4-ethylenedioxythiophene, hereinafter called PEDOT) are practically used.
Of them, PEDOT, which enables structure control by introducing a substituent group, has high conductivity, excellent stability in air, and heat resistance. It is in practical use as antistatic material for photographic film and is widely used as cathode material for electrolytic capacitor (see non-patent document 1).
However, PEDOT which is now commercially available has high performance in film depositing using polyelectrolyte (polystyrene sulfonic acid, hereinafter called PSS), as a dopant. Thus, the conductivity decreases by 2 to 3 than the case a low molecular dopant is used. Therefore, the purpose is limited and it has been desired to provide improvement.
On the other hand, when forming a PEDOT/PSS film by using PSS to the PEDOT, it is known that the conductivity of the PEDOT/PSS film improved by adding dimethyl sulfoxide (hereinafter called DMSO), a polar solvent.
However, in the way of adding DMSO, the production cost is increased since DMSO is expensive. In addition, when removing the remaining solvent after adding DMSO in the manufacturing process, the treating cost is increased because DMSO boils at high point. Moreover, a small amount of DMSO remains on the film so that there is a problem of stability of properties after forming a film.
Heretofore, the applicant has suggested a method of producing a conductive organic film in which a pair of electrodes is received in a reaction vessel, a polymerization solution made by aniline and supercritical carbon dioxide is introduced into the reaction vessel, a surfactant is introduced thereinto to make an emulsion, and then a polyaniline film is deposited on a member to be treated, one of the electrode, under supercritical state (for example, patent document 1).
However, above-mentioned method of conductive organic film requires expensive aniline and a power source. The operation of deposition is complicated, and thus the production cost is increased. Further, the conductivity of the polyaniline film is about 5 S/cm, which is substantially low.    [Non-patent document 1] Kobayashi, Yukio. ‘Doudenseikoubunshi no Saishin Ouyou Gijyutsu [New Applied Technology of Conductive Polymer]’ 2004 Apr. 30 (First Edition) CMC Publishing. Page. 17-18.    [Patent Document 1] Japanese Published Unexamined Patent Application No. 2004-143570